Three teachers had been injured following an explosion targeted their bus at Sheikh Zuweid in North Sinai Governorate on Monday, Youm7 news reported. Unidentified assailants have planted an explosive device on the road side links Sheikh Zueid and Arish city, which led to the injury of three of them, security source told Youm7. The militants attacked the ambulance that tried to help the wounded teachers as well. "Terrorists targeted a security patrol, but they blew the bomb at the time the bus was passing on the road," the security source added. Teachers were admitted to hospital, and security forces are intensifying their search to arrest the offenders.